I have copied here the Wikipedia entry reviewing the history of the UN Secretary General post.
The Security Council has just selected South Korean Ban Ki-Moon for the post of UN Secretary General–the leader of both the free and unfree world.
As the chart shows, the post has moved fitfully between continents.
Early on in the deliberations, many agreed that it was now Asia’s turn. However, U.S. Acting Ambassador John Bolton argued that the job should go to the best qualified candidate regardless of nationality. The United States ultimately agreed to the selection of an Asian SG, albeit one from a historic American ally. One hopes that, when it is North America’s turn, the United States will remember its earlier preference for a wholly merits-based approach. Who knows? The best person for the job then might be an African, a European, or an Asian.